code: def coh_signal_gen():
      """Generate an oscillating signal.
  
      Returns
      -------
      signal : ndarray
          The generated signal.
      """
      t_rand = 0.001  # Variation in the instantaneous frequency of the signal
      std = (
          0.1  # Std-dev of the random fluctuations added to the signal
      )
      base_freq = 10.0  # Base frequency of the oscillators in Hertz
      n_times = len(times)
  
      # Generate an oscillator with varying frequency and phase lag.
      signal = np.sin(
          2.0
          * np.pi
          * (
              base_freq * np.arange(n_times) / sfreq
              + np.cumsum(t_rand * rand.randn(n_times))
          )
      )
  
      # Add some random fluctuations to the signal.
      signal += std * rand.randn(n_times)
  
      # Scale the signal to be in the right order of magnitude (~100 nAm)
      # for MEG data.
      signal *= 100e-9
  
      return signal
  
file_path: mne-python/tutorials/simulation/80_dics.py
imports: import numpy
  from matplotlib import pyplot
  from scipy.signal import coherence, unit_impulse, welch
  import mne
  from mne.beamformer import apply_dics_csd, make_dics
  from mne.datasets import sample
  from mne.minimum_norm import apply_inverse, make_inverse_operator
  from mne.simulation import add_noise, simulate_raw
  from mne.time_frequency import csd_morlet
label_desc: Use image node_id 1 for calling a global function with example usage: coh_signal_gen() and returns: signal